CVE-2018-0132 in IOS XR
Summary
by MITRE
A vulnerability in the forwarding information base (FIB) code of Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause inconsistency between the routing information base (RIB) and the FIB, resulting in a denial of service (DoS) condition. The vulnerability is due to incorrect processing of extremely long routing updates. An attacker could exploit this vulnerability by sending a large routing update. A successful exploit could allow the attacker to trigger inconsistency between the FIB and the RIB, resulting in a DoS condition. Cisco Bug IDs: CSCus84718.
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Analysis
by VulDB Data Team • 02/02/2021
The vulnerability described in CVE-2018-0132 represents a critical flaw in Cisco IOS XR Software's forwarding information base implementation that exposes network infrastructure to remote denial of service attacks. This vulnerability specifically affects the routing information base and forwarding information base synchronization mechanisms within the IOS XR operating system, which is commonly deployed in service provider networks and enterprise core routers. The flaw arises from inadequate handling of routing update processing, creating a condition where malformed or exceptionally large routing updates can disrupt normal network operations. The vulnerability impacts devices running IOS XR Software versions prior to 5.3.4, making it particularly concerning for organizations maintaining legacy network infrastructure. The Cisco Bug ID CSCus84718 documents this specific issue within the company's internal tracking systems, indicating the severity and complexity of the underlying code defect.
The technical root cause of this vulnerability lies in the improper handling of routing update processing within the FIB module of IOS XR Software. When the system receives extremely long routing updates, the code fails to properly validate or process the incoming data structures, leading to inconsistencies between the routing information base and the forwarding information base. This inconsistency creates a cascading effect where the router's internal routing tables become desynchronized, causing the device to malfunction and potentially enter a state where it cannot properly forward traffic. The vulnerability operates at the network control plane level, specifically targeting the routing protocols and table management functions that are fundamental to router operation. The flaw essentially allows an attacker to craft routing updates that, when processed by the vulnerable software, trigger memory management issues or buffer overflows within the FIB processing code. This type of vulnerability falls under CWE-129, which describes improper validation of the length or size of input data, and represents a classic example of how input validation failures can lead to denial of service conditions in network infrastructure software.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire network infrastructure that relies on affected IOS XR devices. An unauthenticated remote attacker can exploit this vulnerability without requiring any credentials or privileged access, making it particularly dangerous in publicly accessible network environments. The DoS condition triggered by this vulnerability can result in complete network outages or partial service degradation, affecting routing decisions and traffic forwarding throughout the affected network segments. Network operators may experience extended periods of service disruption while attempting to recover from the inconsistency conditions, potentially leading to cascading failures across interconnected network devices. The vulnerability's exploitation does not require specialized tools or deep technical knowledge, as standard network traffic manipulation techniques can be employed to craft the malicious routing updates. This accessibility increases the likelihood of exploitation in real-world scenarios, particularly in environments where network devices are not properly segmented or monitored for anomalous routing behavior.
Mitigation strategies for CVE-2018-0132 focus primarily on software updates and network segmentation measures to prevent exploitation. Organizations should immediately apply the relevant security patches provided by Cisco, specifically targeting IOS XR Software versions 5.3.4 and later, which contain fixes for the FIB processing inconsistencies. Network administrators should implement strict routing update filtering mechanisms at network boundaries to prevent malformed routing updates from reaching vulnerable devices. The implementation of BGP route filtering and prefix length validation can help reduce the attack surface by limiting the size and complexity of routing updates that can be processed. Additionally, monitoring systems should be configured to detect unusual routing update patterns that may indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to techniques involving denial of service through resource exhaustion and protocol manipulation, specifically targeting the network infrastructure layer. Organizations should also consider implementing redundant routing paths and failover mechanisms to minimize the impact of potential exploitation, while maintaining detailed logging of routing table changes to aid in forensic analysis if an attack occurs. The vulnerability demonstrates the critical importance of proper input validation in network infrastructure software and highlights the need for comprehensive security testing of routing protocols and control plane implementations.